[aspect-devel] Problem: Iterative advection solver does not converge

[Wolfgang Bangerth]

On 06/06/2016 12:50 PM, John Naliboff wrote:
>
> Ouch - The residual in the last step was 1.99733e+21.  Something is definitely
> amiss ;)

John already asks all of the right questions, but I did wanted to comment on 
this: the residual is like a right hand side vector, which is an integral over 
cells. The mesh size here is around 1e5 meters, so the integral already has a 
factor of 1e15 just by the volume of each cell. Depending on what the average 
values of the integrand are, 1.997e21 may or may not actually be a large residual.

Ultimately, what matters is how it compares to the starting residual.

Best
  Wolfgang


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Wolfgang Bangerth               email:            bangerth at math.tamu.edu
                                 www: http://www.math.tamu.edu/~bangerth/